Viscosity index improvement of lubricating oil fractions

ABSTRACT

A METHOD OF IMPROVING THE VISCOSITY INDEX (vI) OF HYDROCARBON LUBRICATING OIL FRACTIONS COMPRISING ESSENTIALLY COMPLETELY ABSORBING A HYDROCARBON LUBRICATING CHARGE OIL, E.G., A SOLVENT EXTRACT RECOVERED FROM AN EXTRACT PHASE EXITING FROM EXTRACTION ZONE IN SOLVENT REFINING OF LUBRICATING OIL, ON A SOLID ABSORBENT, SELECTIVELY ELUTING THE OIL CONTAINING SOLID ABSORBENT WITH AT LEAST ONE LIQUID SOLVNET HAVING A DIELECTRIC CONSTANT OF LESS THAN ABOUT 15, RECOVERING FROM THE RESULTANT ELUTION SOLUTION AN ELUATE LUBE OIL FRACTION OF HIGHER VISCOSITY INDEX THAN THE CHARGE OIL AND HYDROREFINING THE RECOVERED HIGHER VISCOSITY INDEX ELUATE OIL FRACTION TO FORM A HYDROREFINED OIL FRACTION OF A VISCOSITY INDEX GREATER THAN SAID ELUATE OIL FRACTION.

United States Patent Office 3,830,730 Patented Aug. 20, 1974 3,830,730 VISCOSITY INDEX IMPROVEMENT F LUBRICATING OIL FRACTIONS Theodore C. Mead, Port Arthur, and Norman R. Odell,

Nederland, Tex., and Robert F. Benson, Fayetteville, Ara, assignors to Texaco Inc., New York, NY. No Drawing. Filed Apr. 7, 1972, Ser. No. 242,143 Int. Cl. 010g 31/14, 23/02, 43/08 US. Cl. 208144 6 Claims ABSTRACT or THE DISCLOSURE v.A method-of improving the Viscosity Index (VI) of hydrocarbon'lubricating oil fractions comprising essentially completely absorbing a hydrocarbon lubricating charge oil, e.g., a solvent extract recovered from an VI fractions, e.g., of less than about 5 VI resulting from lube oil refining such as the solvent refining extracts into oils of intermediate viscosity index since the present day intermediate oil often contains in part higher VI fractions to compensate for their low VI components. The higher VI fractions find better economic use in the premium automotive oils than in upgrading oil fractions to an extract phase exiting from the extraction zone in solvent refining of lubricating oil, on a solid absorbent, selectively eluting the oil containing solid absorbent with at least one liquid solvent having a dielectric constant of less than about 15, recovering from the resultant elution solution an eluate lube oil fraction of higher viscosity index than the charge oil and hydrorefining the recovered higher viscosity index eluate oil fraction to form a hydrorefined oil fraction of a viscosity index greater than said eluate oil fraction.

BACKGROUND OF INVENTION 'This invention relates to the production of lubricating oils. More particularly, it is concerned with a method of producing lubricating oil fractions of improved viscosity index (VI).

Generally, it has been established that the saturated components (the paraffins and naphthenes) of a lubricating oil are the high viscosity index (VI) components and the aromatic components are in general the low VI components with olefinic components residing in between. Further, it has been found that components Within each fraction have varying viscosity indexes.

Various processes are available for the refining of lubricating oil charge stock, that is, upgrading its VI, lowering pour, improving color, etc. Conventionally, the lube oil stock obtained either by vacuum distillation or by deasphalting a vacuum residuum can be improved by solvent extraction to increase VI and by solvent dewaxing to lower the pour point. Acid treating may be used to improve color, stability and the resistance of the oil ,to oxidation and clay contacting has been used to improve the color and to neutralize the acid treatment. More recently, severe catalytic hydrogenation of the oil has been proposed as a substitute for solvent refining to increase .the viscosity index of the oil. However, the resultant oil product is not stable towards ultraviolet light and with certainfeed stocks relatively low yields are obtained.

It has been customary in the past to increase the viscosity index of finished lubricating oils, particularly crankcase oils, by the addition thereto of viscosity index improvers such as the polyalkylmethacrylates. The mush rooming demands for wide temperature range automatic transmission fluids and wide multigrade motor oilsof .ever higher VI are requiring the use of viscosity index improving additives in amounts fast approaching levels 'whichoften result in substantially negative effects-such .as decreased shear stability, increased corrosion and in .situ polymerization. There is, therefore, an increasing need in lube oil refining to recover the maximum amount of the higher VI fractions and to further upgrade the VI of therecovered fractions in order to reduce the amount of VI improving additives required. In addition, there is acontinuing search for processes to upgrade the lower intermediate level.

It is an object of this invention to produce lubricating fractions of substantially improved VI, particularly from low quality (low VI) lubricating oil charge stocks such as the highly aromatic extracts derived from solvent refining. Another object is to produce lubricating oil fractions of substantially higher viscosity than the initial charge stock wherein the maximum amount of high VI components are recovered from said charge stock coupled with the conversion of the recovered fractions into still higher VI fractions. Still another object is to produce lubricating oils which are of improved stability to ultraviolet light. These and other objects will be obvious to those skilled in the art from the following disclosure:

SUMMARY OF INVENTION Broadly, our method comprises substantially completely absorbing a charge hydrocarbon lubricating oil on a solid absorbent, then eluting the absorbent with a liquid eluent selective for the higher VI components in the absorbed oil to produce an elution solution containing as the eluate an oil fraction of greater VI than said charge oil, recovering from the resultant elution solution the eluate oil fraction, contacting said fraction with a hydrorefining catalyst under hydrorefining conditions and recovering the hydrorefined hydrocarbon oil of further improved VI. One embodiment of the method comprises first subjecting the lubricating oil charge stock to solvent refining to produce a raflinate rich in paraflins and naphthenes and a solvent extract rich in aromatics, contacting the solvent extract with a solid absorbent and hydrorefining catalyst as heretofore described and optionally combining at least a portion of the hydrorefined extract With said rafiinate or recycling the solvent to the solvent refining zone.

DETAILED DESCRIPTION OF THE INVENTION More specifically, the method comprises contacting a hydrocarbon lubricating charge oil with a fixed bed of solid absorbent of a particle size of between about 20 and 200 mesh (US. Standard) in a manner to substantially completely absorb the charge oil on the solid absorbent. This contacting is accomplished by standard means such as percolating the charge oil through a fixed bed column of solid absorbent, the column being advantageously of dimensions of a length to diameter ratio of between about 50:1 and 5:1, preferably between about 30:1 and 20:1, utilizing a solid absorbent to charge oil weight ratio of between about 10:1 and 1:1, preferably between 3:1 and 2: 1. The loading of the oil on the absorbent is normally accomplished at an ambient temperature but temperatures between about 50 and 300 F. may be employed. In order to facilitate the contact of the charge oil with the solid absorbent, particularly when said charge oil is of relatively high viscosity, i.e., above about cs. at 100 F., the fraction'may be diluted with liquid hydrocarbon solvent of low polarity, that is, one having a dielectric constant of less'than about 15 at 77. F. and boiling below about 250 F., in a quantity to facilitate As a next step-the oil-loaded solid absorbent is washed, that is, eluted with a liquid hydrocarbon eluent having a dielectric constant below about 15 at 77 "F., and a boiling point below 250 F. at a temperature between about 20 and 250'F., preferably at about 70-80 F.'in

an eluent quantity sufficient to recover from the oil loaded absorbent, as the eluate, an oil fraction of higher viscosity index than the charge oil, advantageously utilizing an eluent to initial absorbed oil weight ratio of between about 50:1 and 1:1, preferably between about 20:1 and 5:1. The exact amount of eluent required will depend on many variables such as VI desired, eluent, eluate, temperature, absorbent, etc. The eluent is normally introduced in the top area of the absorbent column with the elution solution exiting from the bottom area. The exiting elution solution is then fractionated by standard means such as via distillation to separate the eluent solvent from the eluate oil of a VI higher than the initial absorbed oil. In one embodiment of the method the fixed bed may be successively eluted with eluent of the same polarity or of increasing polarity followed by the optional combining of the recovered eluate fraction or portions thereof depending on the VI desired.

In the elution phase of the method as the polarity of the fractions comprising the charge oil increases their VI and their readiness to desorb decreases. Further, as the polarity of the eluent increases the eluents ability to desorb increases. Therefore, successive elutions of the oil loaded absorbent with the same eluent or with eluents with increasing polarity will result in successive fractions of eluate oil of decreasing VI.

Examples of suitable hydrocarbon oil charge stock are those having "viscosities between about 3 and 50 cs. at 210 F. Although the invention is applicable to any lubricating oil charge stock, it is particularly suitable for the solvent extracts resulting from the solvent refining or lubricating oil particularly those having VI below about 20. Other suitable charge stocks are those of medium quality, that is, charge stocks having a VI not greater than about 90, more preferably below 80. Examples of these latter charge stocks are non-solvent refined dewaxed lubricating oils of a viscosity of between about 50 and 250 cs. at 100 F. and low VI lube oil rafiinates from solvent refining. The lubricating oil stocks are initially obtained from the distillation of crude petroleum. The stock may be obtained as overhead from a vacuum distillation or may be obtained from the residue of vacuum distillation by deasphalting the residue by contact, for example, with a deasphalting agent such as propane, butane and the like and mixtures thereof.

The solid absorbents employed are those materials of high surface areas having a mesh size (U.S. Standard) of between about 20 and 200. Suitable examples of such materials are bauxite, calcined bauxite, alumina oxide, silicon oxide, clay, bentonite, diatomaceous earth, Fullers earth, bone char, charcoal, magnesium silicate, activated Kaolin, silica-alumina and zeolites. The preferred material is calcined bauxite, a commercial version sold under the trade name Porocel.

Specific examples of the eluents contemplated herein listed roughly in the order of increasing eluting power are isopentane, hexane, cyclohexane, naphtha, benzene, toluene and xylene. Preferred solvents are naphtha and cyclohexane.

-It is to be noted when the desired oil has been eluted from the column of the absorbent it is advantageous to regenerate said column by desorbing the low VI, highly aromatic polar residues by eluting the column with highly polar liquid solvents i.e. having a dielectric constant substantially above 15 and then steaming the column to remove the residual eluting solvent. Examples of suitable highly polar solvents are methylethylketone, acetone and liquid alkanols.

Solid absorbent fractionation operates on the principle that the employed solid absorbent material has an increasing affinity for components of increasing polarity. The components of the highest polarity (lowest VI) are the aromatics and these are the most tightly held by the solid absorbent. A more detailed order of increasing absorbability (decreasing VI and increasing polarity) is as 7 follows: parafiins, naphthenes, olefins and aromatics. In the elution, as eluent polarity increases, the ability of the eluent to desorb increases, and as the polarity of the ab-- sorbed oil fraction increases, its ability to be desorbed decreases. The particular selection of the eluent to be utilized will be dependent on the average VI of the desorbed oil desired.

In a preferred embodiment of the process, the charge oil to the solvent absorbent is a solvent extract derived from a solvent refining zone. The lubricating oil stock charged to the solvent refining zone is ordinarily obtained from the distillation of crude petroleum, such as overhead from vacuum distillation or from the vacuum distillation residue by deasphalting with an agent such as propane, butane and the like and mixtures thereof. According to our preferred embodiment process, the lubricating oil is charged to solvent refining zone and is subjected to solvent extraction using a solvent having an affinityfor aromatic hydrocarbons. Particularly suitable solvents include furfural, phenol, dichloroethyl ether and N-methyl- 2-pyrrolidone. Advantageously, the solvent extraction is carried out utilizing a countercurrent flow technique, the solvent being introduced at the top of the extraction tower and the oil near the bottom with the tower being maintained at a temperature between about 125 and 250 F. The solvent-oil ratio may range between about 1:1 to 6:1 by volume. Oil is recovered from the top of the tower as raflinate and is advantageously further processed byheating and stripping to remove residual solvent. Solvent and solvent extract are removed from the bottom area of the extraction tower and are normally separated by distillation. Typical solvent extracts recovered have the following properties:

Property: Range Gravity, API 8.0 to 19.9. Flash, COC, F 390 to 545. SUS at 210 F. 45 to 570. Viscosity Index 50 to'+50. Pour, F 0 to 100.

RI at 77 F 1.47 to 1.55.

The recovered solvent extract is then subjected to the solid absorption stage as heretofore described.

As a final stage of the process, irrespective whether or not the optional preliminary solvent refining stage is employed, the eluted oil fraction of improved VI recovered from the solid absorption stage is subject to catalytic hydrogenation (hydrorefining) at a temperature between about 550 F. and 1000 F., preferably between about 775 and 825 F., under a hydrogen pressure of between about 750-5000 p.s.i., preferably between about 1500 and 2500 p.s.i., utilizing an hourly space velocity (v./v./hr.) of between about 0.1 and 4 volumes of oil per volume of catalyst per hour, preferably between about 0.5 and 1.5 v./v./hr., with a hydrogen dosage of between about 1000 and 10,000 standard cubic feet per barrel per hour (s.c.f.b.), preferably between about 2500 and 750 s.c.f.b. The hydrogen gas used for the hydrogenation need not necessarily be of pure hydrogen, hydrogen having a purity of at least about 65 volume percent, preferably at least about volume percent, may be employed.

The catalyst employed in the hydrorefining step generally comprises a hydrogenation component carried on a support. The principle ingredient of the hydrogenation component is a Group VIII metal or mixtures of Group VIII metals or compounds thereof such as the oxides or sulfides. Examples of Group VIII metals which may be used in the hydrogenating component are nickel, cobalt and iron or mixtures thereof. The iron group metal should be present in an amount between about 2 and 40 wt. percent, preferably between about 2 and 15 wt. percent, based on the total weight of the catalyst composite. In conjunction with the iron group metal, a Group VI metal such as molybdenum or tungsten may be used. Insuch case the Group VI metal may be present in an amount between about 5 and 40 wt. percent based on the weight of the composite, a preferred range being between about and 30 wt. percent.

The hydrogenating catalyst component is carried on a base comprising a refractory inorganic oxide material such as alumina, silica, magnesia, zirconia, titania, crystalline alumino silicates and the like and mixtures thereof. When the lubricating oil extract introduced into the hydrorefining zone is derived from a deasphalted residuum and it is the desire to upgrade the extract to a maximum VI, then. advantageously the catalyst has an acidic support such as acrystalline alumino silicate of the Zeolite Y type of reduced alkali metal content, e.'g., less than 1 wt." percent composited with a mixture of an amorphous inorganic oxide-material such as 70-90 wt. percent s1l1ca and 10-30 wt. percent alumina. If the extract has been obtained originally from a wax distillate based stock, then advantageously the catalyst support would have little, if any, cracking ability. 3 If the catalyst has cracking activity which on occasion, it may desire to suppress, then a small amount of ammonia or carbon monoxide may be added to the hydrogen. Asuitable amount, depending on the extent to which the cracking is to be suppressed will range between about 0.1 and 2 wt. percent ammonia or carbon monoxide basis reactive feed gas. T hecatalyst may be used in the form of a slurry, a fluidized bed or a fixed bed. When used in the form of a fixedbed, the oil and hydrogen flow may be either upward or downward or the flow of hydrogen may be countercurrent to the downward flow of oil. In broad terms, the hydrorefining catalyst covered by the scope of this invention are those which have suitable activity for carrying out the reactions described herein. Included are those containing from 2 to 10% cobalt or nickel and 10 to 30 wt. percent'molybdenum or tungsten. Particularly suitable catalysts are those containing about 6 wt. percent nickel and wt. percent tungsten or about 5 wt. percent nickel or cobalt and about 12-15 wt. percent molybdenum.

In one embodiment of the invention the hydrorefined product after being subjected to a separation treatment for the removal of hydrogen and light distillates can be recycled to the solvent refining zone (when employed) into which it is introduced with fresh feed. In another embodiment of the invention the hydrorefined product after separation of the lighter materials can be combined with the raflinate from the solvent extraction zone (when employed) with the combined stream by being subjected to solvent dewaxing if dewaxing has not been previously undertaken. And in still another embodiment the hydrorefined oil-product may be utilized directly as high or intermediate VI oil depending on the particular VI thereof.

To improve the pour point ofthe oil product, there :can be included in the process of the invention normally :either a preliminary treatment of the initial charge oil or as a final treatment step of the hydrorefined product alone or in combination with other oil fractions such as a solvent extraction rafiinate, the contacting of the oil with a dewaxing agent such as a mixture of equal parts of ketone, for example, acetone or methylethylketone and an aromatic compound suchas benzene or toluene in a ratio of about 3 to 4 parts by volume of solvent per volume of oil. The mixture is cooled to a temperature of about 0 to 20 F. depending on the desired pour point and the 'waxy components are removed from the chilled mixture by filtering or by centrifuging. The dewaxed liquid is then subjected to flash distillation and stripping to remove the solvent.

T 'The 'following examples further illustrate the method fvv'asj separated from a paraflinic crude oil by vacuum distillation and solvent dewaxed to a '30F. pour. Tests 6 on the dewaxed Wax Distillate A found a kinematic viscosity at F. of 130.51 es. and a VI of 56.

1 Solvent Extraction Zone t In a solvent extraction zone dewaxed WaxDistillate A was solvent extracted in a single stage batch extraction apparatus utilizing N-methyl-2-pyrrolidone as the solvent, a solvent dosage of 208%, and an extraction temperature of F. The raffinate oil was recovered as the upper layer and the solvent extract in a lower layer solvent extract solution. The solvent extract solution was subjected to distillation at a temperature of about 410 F. and the N-methyl-Z-pyrrolidone solvent was collected as overhead leaving as residue a material identified as dewaxed Wax Distillate A solvent extract having a kinematic viscosity at 100 F. of 113.3 cs. and a viscosity index of -3.

Solid Fractionation Zone To a column of calcined bauxite having a length of 25 times its diameter, weighing 16 kilograms and of a 20- 200 mesh particle size, there was introduced in the upper portion 2902 grams of said dewaxed Wax Distillate A solvent extract diluted with 15 kilograms of cyclohexane. The absorption was conducted at 75 F. When the thus introduced extract was essentially completely absorbed on the column of bauxite, there was then introduced at the top of the column and sequentially passed therethrough at a rate of 10 cos. per minute at 75 F. 29 kilograms of cyclohexane, 14.5 kilograms benzene and 14.1 kilograms methylethylketone. The cyclohexane fraction was collected in an amount of 3600 grams and stripped under reduced pressure to remove cyclohexane as overhead. The residual eluted oil weighed 904 grams and was determined to have a kinematic viscosity of 58.43 cs. at 100 F. and a viscosity index of 56. This represented a 31% recovery of material with a VI improvement of 59 VI units basis oil charged to solid absorbent. All oil remaining on the solid absorbent after the cyclohexane absorption was removedv and recovered on a quantative basis with the benzene and methylethylketone elutions.

Hydrorefining Zone The 56 VI fraction eluted from the solid absorbent zone was forwarded to a hydrorefining zone and contacted with a catalyst composed of 6 wt. percent nickel and 21 wt. percent tungsten sulfiide supported on a silicaalumina carrier at a temperature of 825 F. under a hydrogen pressure of 1800 psi. utilizing a space velocity of 1 volume charge oil per volume catalyst per hour and a hydrogen dosage of 5000 s.c.f.b.

The weight and properties of the hydrogenated fraction and comparison between the initial charge oil, the eluted oil and hydrogenated oil were as follows:

Using the same procedure as Example I, a moderate viscosity cut from dewaxed Wax Distillate A solvent extract of the following properties:

Weight 2472 grams. Vlscoslty 528.73 centistokes at 100 F. Viscosity Index -55.

was charged to the bauxite column There was obtained an eluted oil fraction of the following amount and properties.

Weight 720 grams. a Viscosity 133.94 centistokes at 100 F. Viscosity Index 39. I

This represents a 29 wt. percent recovery of material with a VI improvement of 94 VI units basis oil fraction charge to the solid absorbent. The eluted oil was then hydrorefined.

The weight and properties of the hydrogenated fraction and comparison between the charge oil, the eluted oil and hydrogenated oil were as follows:

Charge Charge Hydroto solid to hydrogenatetl Tests absorber genator fraction VI increase 94 126 EXAMPLE III Utilizing the same procedure of Example I, a high viscosity cut from dewaxed Wax Distillate A solvent extract fraction of the following amount and properties.

Weight 2060 grams. Viscosity 3787.5 centistokes at 100 F. Viscosity Index 140.

was charged to the bauxite column. There was obtained an eluted oil fraction of the following amount and properties;

Weight 707 grams. Viscosity 469.29 centistokes at 100 F. Viscosity Index 9.

This represents a 24 wt. percent recovery of material with a VI improvement of 149 units. The eluted oil was then hydrorefined.

The weight and properties of the hydrogenated fraction and comparison between the charge oil, the eluted oil and hydrogenated oil were as follows:

This procedure represents an example of the upgrading of already high quality lubricating oil.

The procedure of Example I was essentially employed with the exception that the raffinate from the solvent extraction was charged to the bauxite column rather than the solvent extract. Further, the bauxite was eluted sequentially with 8.4, 10.2 and 19.6 liter portions of cyclohexane and then with liters methylethylketone to recover four fractions of desorbed oil.

The rafiinate loaded on to the bauxite absorbent was of the following amounts and properties.

Weight 2796 grams. Viscosity 147.95 centistokes at 100 F. Viscosity Index 88.

There was obtained (1) a first cyclohexane eluted oil fraction of the following weight and properties:

Weight 813 grams. Viscosity 116.43 centistokes at 100 F. Viscosity Index 97.

(2) a second cyclohexane eluted oil fraction of the following weight and properties:

Weight 865 grams. Viscosity 133.66 centistokes at 100 F. Viscosity Index 94.

(3) a third cyclohexane eluted oil fraction a desorbed oil of the following weight and properties:

Weight 925 grams. Viscosity 177.71 centistokes at 100 F. Viscosity Index 86.

and (4) a fourth methylethylketone eluted oil fraction was of the following weight and properties:

Weight 193.5 grams. Viscosity Viscosity Index 32.

The first fraction showed a 29 wt. percent recovery of initial material in which the viscosity index had been improved by 9 units. The first fraction was hydrorefined.

The weight and properties of the hydrogenated first fraction and comparison between charge 'oil, eluted oil and hydrogenated first fraction were as follows:

Charge to Hydro- Charge to to hydrogenated Tests absorber genator fraction EXAMPLE V Weight 920 grams. Viscosity 173 centistokes at F. Viscosity Index 49.

The eluate oil fraction recovered from the cyclohexane elution solution was of the following weight and prop erties:

Weight 314 grams. Viscosity 133.26 centistokes at 100 F. Viscosity Index 63.

This represented a 34 wt. percent recovery basis initial absorbed oil of a viscosity index 14 units higher than charged. The eluate was then hydrorefined.

The weight and properties of the hydrogenated fraction and comparison between the charge oil, eluted oil and hydrogenated oil were as follows:

Charge to Hydro- Charge to to hydrogenated Tests absorber genator fraction Vlsc., cs. at 100 F 174 133.26 44. 95 VI 49 63 88 Grams 1, 000 340 313 VI increase 14 39 We claim:

1. A process for the production of a lubricating oil fraction of improved viscosity index which comprises:

(a) introducing hydrocarbon lubricating oil charge into the upper portion of a fixed bed absorbent, said charge oil being selected from the group consisting of a dewaxed distillate fraction and a solvent-refined extract derived from solvent refining a lubricating oil fraction, said absorbent comprising calcined bauxite having a particle size between about 20 and 200 mesh, at a temperature between about 50 and 300 'F., utilizing a weight ratio of said absorbent to said charge oil of between about 10:1 and 1:1,

(b) eluting said absorbent with liquid cyclohexane at a temperature between about 50 and 300 F. and at a weight ratio of cyclohexane to oil of between about 50:1 and 1:1, to elute from said absorbent an eluate oil fraction having a viscosity index greater than the charge oil,

(c) contacting said eluate oil fraction in a hydrogenation zone with hydrogen and with a hydrogenation catalyst selected trom the group consisting of Group VI metal, Group VHI metal, mixtures of Group VI and Group VIII metals or compounds thereof supported on alumina-silica to hydrogenate said eluate oil fraction at a temperature between about 550 and 1000 F. at a pressure between about 750 and 5000 p.s.i. at a space velocity between about 0.1 and 4 volumes oil/volume catalyst and a hydrogen dosage of between about 1000 and 10,000 s.c.f.b./hr. and recovering from the hydrogenation zone a lubricating oil fraction of a greater viscosity index than said eluate oil fraction.

2. A method in accordance with Claim 1 wherein said charge oil is a solvent-refined extract derived from solvent refined lubricating oil.

'3. A method in accordance with Claim 1 wherein said charge oil is a solvent-refined extract derived from a solvent refined lubricating oil and said eluting step (b) comprises sequentially contacting said solid absorbent with cyclohexane and then with benzene.

4. A method in accordance with Claim 1 wherein said lubricating oil charge is a dewaxed distillate lubricating oil fraction.

5. A process for the production of a lubricating oil fraction of improved viscosity index which comprises:

(a) passing a hydrocarbon lubricating oil charge through a solvent extraction zone maintained at a temperature between about 125 and 250 F. to form aromatic-rich solvent extract and a saturated aliphatic-rich reafiinate, said solvent being between about 100 and 600 volume percent of said oil charge and being selected from the group consisting of furfural, phenol, dichloroethyl ether, and N-methyl-2- pyrrolidone,

(b) introducing said aromatic-rich solvent extract into the upper portion of a fixed bed absorbent column, said absorbent comprising calcined bauxite of a particle size between about 20 and 200 mesh, said solvent extract being absorbed at a temperature between about 50 and 350 F., utilizing a weight ratio 10 of said absorbent to said extract of between about 10:1 and 1:1,

(c) eluting said absorbent with liquid cyclohexane at a temperature between about and 300 F. and at a weight ratio of cyclohexane to oil of between about 50:1 and 1:1, to elute from said absorbent an eluate oil fraction having a viscosity index greater than the charge oil,

(d) contacting said eluate oil fraction in a hydrogenation zone with hydrogen and with a hydrogenation catalyst selected from the group consisting of Group VI metal, Group VIII metal, mixtures of Group VI and Group VIII metals or compounds thereof supported on alumina-silica to hydrogenate said eluate oil fraction at a temperature between about 550 and 1000 F. at a pressure between about 750 and 5000 p.s.i. at a space velocity between about 0.1 and 4 volumes oil/volume catalyst and a hydrogen dosage of between about 1000 and 10,000 s.c.f.b./hr. and recovering from the hydrogenation zone a lubricating oil fraction of a greater viscosity index than said eluate oil fraction.

6. A method in accordance with Claim 5 where said charge oil is a solvent refined extract derived from a solvent refined lubricating oil and said eluting step (b) comprises sequentially contacting said solid absorbent with cyclohexane and then with benezene.

References Cited UNITED STATES PATENTS 3,201,344 8/ 1965 Broughton 208-264 3,328,293 6/1967 Brenken 208264 2,967,144 1/ 1961 Cole 208-87 3,256,175 6/ 1966 Kozlowski et a1. 208264 3,438,887 4/ 1969 Morris et al 208-87 DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner US. Cl. X.R. 208-87; 21 1 mg v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,830,730 Dated August 20, 1974 Inventofla) THEODORE C. MEAD, NORMAN RNODELL and ROBERT F. BENSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, line 31, "or" should read --of--. Col. 4, line '57, "750" should read 7500-.

Col. 7, line 42, "653.1" should read --65.3l-.

Col. 9, line 32, "reaffinate" should read --raffinate--.

Signed and sealed this 29th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

